Isolators

ABSTRACT

An isolator comprises an enclosure member adapted to provide a controlled microbiological environment and having a transfer port for passage of objects into and out of the enclosure member. The transfer port comprises a conduit communicating at one end with the interior of the enclosure member, and having its other end external to the enclosure member, and air supply means communicating with the conduit to direct a flow of sterilised air over the inner surface of the conduit. Preferably the conduit has an inner wall and an outer wall spaced apart over at least part of the conduit, and there is provided an array of openings distributed over the inner surface of the conduit.

United States Patent Trexler 1 Apr. 8, 1975 [54] ISOLATORS 3,692,024 9/l972 von Otto l28/l32 Inventor: Philip Charles Trader sindlesham 3.709.210 l/ I973 Matthews 128/ 191 A England Primary Examiner-Richard A. Gaudet [73] Assignee: National Research Development Assistant Examiner-G. F. Dunne Corporation, London. England Attorney, Agent, or Firm-Cushman, Darby & Cushman [57] ABSTRACT An isolator comprises an enclosure member adapted to provide a controlled microbiological environment and having a transfer port for passage of objects into and out of the enclosure member. The transfer port comprises a conduit communicating at one end with the interior of the enclosure member. and having its other end external to the enclosure member, and air supply means communicating with the conduit to direct a flow of sterilised air over the inner surface of the conduit. Preferably the conduit has an inner wall and an outer wall spaced apart over at least part of the conduit, and there is provided an array of openings distributed over the inner surface of the conduit,

l8 Claims, 4 Drawing Figures ISOLATORS The present invention is concerned with improvements in and relating to isolators.

The invention is concerned with enclosures which have become known as isolators and which are used for the handling of laboratory animals and human patients under gnotobiotic conditions. An isolator commonly consists of a flexible bag of synthetic plastic material forming an enclosure which is continuously vented with germ free air, and commonly maintained at a small positive air pressure with respect to the ambient atmosphere. Commonly the isolators are in disposable form, being provided presterilised for use on one occasion only.

In such as isolator, the main weakness in the isolation of the system lies in the arrangements for introducing and removing material and instruments into and from the enclosure, as these arrangements usually involve the necessity of breaking the boundary of the environment.

It is an object of the present invention to provide improved arrangements for introducing and removing objects to and from an isolator.

According to the present invention there is provided an isolator comprising an enclosure member and having a transfer port for passage of objects into and out of the enclosure member, the transfer port comprising conduit communicating at one end with the interior of the enclosure member, and having its other end external to the enclosure member, and air supply means communicating with the conduit and arranged of direct a flow of sterilised air over that part of the inner surface of the conduit which adjoins the external end of the conduit in a flow pattern such as substantially to prevent in operation entry of unsterilised air into the con duit.

By an isolator is meant apparatus including or consisting of an enclosure member adapted to provide a controlled microbiological environment for example for medical or experimental purposes. Such an enclosure will commonly have means for handling objects within the enclosure member without breaking the microbiological isolation of the enclosure. The term enclosure member includes a partial enclosure member, for example an open bottomed enclosure member adapted to being secured to the body of a patient to provide in operation a complete enclosure the base of which is constituted by part of the body of the patient.

The air supply means may include an array of openings distributed over the inner surface of the conduit. ln one arrangement the conduit has an inner wall and an outer wall spaced apart over at least part of the conduit, and the air supply means includes an air inlet in the outer wall of the conduit for supplying air to the space between the inner and outer walls of the conduit.

In a preferred arrangement according to the invention an isolator comprises a flexible walled enclosure member having an air inlet for supplying air to inflate the enclosure member in use and having a transfer port for passage of objects into and out of the enclosure member, the transfer port comprising a conduit communicating at one end with the interior of the enclosure member, and having its other end external to the enclosure member. the conduit being made of flexible material and having an inner wall and an outer wall spaced apart over at least part of the conduit, an air inlet in the outer wall of the conduit for supplying air to the space between the inner and outer walls of the conduit, and an array of openings in the inner wall of the conduit for directing a flow of sterilised air over at least part of the inner surface of the conduit in a flow pattern such as substantially to prevent in operation entry of unsterilised air into the conduit.

The conduit walls may be made of flexible material, with the inner and outer walls joined together at intervals to provide inflatable ribs such that the conduit is at least partially self-supporting in an open configuration when inflated through the air inlet.

Thus the size of the openings in relation to the volurne of the space between the walls of the conduit may be such that in operation application to the space of air above ambient pressure inflates the conduit and supports the conduit in an open position. The air chamber may comprise a plurality of ribs aligned along the length of the conduit, and may include circular ribs passing around the ends of the conduit.

ln some arrangements according to the invention, either the inner or outer wall of the conduit may be formed of rigid material, the other wall being flexible, or both the inner and outer walls of the conduit may be formed of rigid material.

For example, where the conduit walls are flexible, the whole transfer port may conveniently be made as a disposable item, being supplied in sterile condition for use on one occasion only. Alternatively, the conduit may be wholly or partly a rigid structure, and may be a reusable item to be coupled to a disposable isolator.

The inner wall of the conduit may be made of woven fabric, the said array of openings being provided by the intersticies in the woven fabric. The said woven fabric may be canvas.

There may be provided a layer of air filtering material positioned between the inner and outer walls of the conduit and contiguous with the inner wall of the conduit.

There may be provided a closure member situated within the enclosure for closing off temporarily the conduit member from the interior of the enclosure member. The closure member may comprise a further conduit of flexible material extending from the first conduit into the inside of the enclosure member. Alternatively, the closure member may comprise a flexible sheet or material hanging across the opening in the isolator wall, and biassed to close the opening by a weight attached to the bottom of the sheet. Alternatively the opening may be closed by flaps with closure means such as a zip fastener.

The invention has particular usefulness where the isolator is a disposable isolator, the enclosure member being made of flexible synthetic plastics material, although the conduit may be made of rigid material.

There is also provided in accordance with the present invention a transfer port for an isolator comprising a conduit having one end adapted to communicate with the interior of an isolator and another end adapted to be positioned exterior to the isolator to allow objects to be passed through the conduit into and out of the isolator, and air supply means communicating with the conduit and arranged to direct a flow of sterilised air over that part of the inner surface of the conduit which adjoins the exterior end of the conduit in a flow pattern such as substantially to prevent in operation entry of unsterilised air into the conduit.

There is further provided in accordance with the present invention a transfer port for an isolator comprising a conduit having one end adapted to communicate with the interior of an isolator, the conduit having an inner wall and an outer wall spaced apart over at least part of the conduit, an air inlet in the outer wall of the conduit for supplying air to the space between the inner and outer walls of the conduit, and an array of openings in the inner wall of the conduit for directing a flow of sterilised air over at least part of the inner surface of the conduit in a flow pattern such as substantially to prevent in operation entry of unsterilised air into the conduit.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. I is a perspective view of a transfer port attached to the boundary wall of an isolator, and embodying the present invention;

FIG. 2 is a longitudinal section of the transfer port of FIG. 1 taken along the lines II II;

FIG. 3 is a perspective view of a modified transfer port embodying the invention; and

FIG. 4 is a longitudinal section, partly diagrammatic, of the transfer port of FIG. 3, taken along the lines IV IV in FIG. 3.

Referring to FIGS. 1 and 2, there is shown a part of a wall 11 of an isolator comprising a flexible enclosure member of synthetic plastics material, such as polyvinylchloride, inflated with sterilised air pumped into the enclosure at a pressure slightly above ambient pressure. Secured to the wall 11 is a transfer port 12 which in the embodiment shown consists of an entry port.

The entry port comprises a conduit 13 having one end 14 sealed around an opening 15 in the wall 11 by a thermo-weld at 16. The opening 15 of the wall 11 is located by a rigid metal ring 17 which in practice is supported by a metal frame of the isolator, not shown in FIG. I. The junction of the conduit end 14 and the wall II at the weld I6 is secured to the rigid ring 17 by adhesive tape 18.

The conduit 13 comprises a substantially cylindrical passageway or sleeve offlexible synthetic plastics material having inner and outer walls 19 and 20 respectively. At the attached end 14 of the conduit the two walls 19 and 20 lie flat together, and the walls are welded together along a number of weld lines, for example shown at 21, in a pattern such as to define a series of longitudinal ribs 22 and a circular end rib 23 running around the free end of the conduit 13. The ribs 22 and 23 are in communication with each other and are in communication with an air input nozzle 24 which is coupled by way ofa sterilizing filter 25 to a pipe 26 leading from an air compressor not shown.

It will be appreciated that all connections and pipes down stream of the filter need to be carefully sterilised before connection, and to be maintained in a sterile condition during operation of the transfer port. In alternative arrangements, the air may be fed unsterilized to the transfer port, and there may be provided a filter located within, or fixed to, the transfer port for filtering the air before it emerges from the openings in the inner wall of the transfer port.

In operation, air is pumped through the air input 24 at a pressure slightly above ambient atmospheric pressure and inflates the ribs 22 and end ring 23 so as to maintain the conduit in an open position. The end walls 19 and 20 in the areas between the ribs 22 lie flat against each other and are not inflated. The weight of the upper wall of the conduit causes the circular end rib 23 to adopt a slightly oval configuration as shown.

Distributed over inner surface of the conduit 13 is an array of openings comprising a plurality of pin prick apertures 27 distributed along the ribs 22 and 23, for directing a flow of sterilised air over the inner surface of the conduit I3. These apertures are so positioned, and the pressure of the air from the pump is so arranged, that the air flowing over the inner surface of the conduit 13 flows in a flow pattern such as substantially to prevent entry of unsterilised air into the isolator 10. That is to say that the air pumped through the apertures 27 flows outwardly along the inner surface of the conduit 13 and thence in a cone of sterilised air leaving at the end ring 23. It will be appreciated that as the isolator 10 is maintained at a pressure slightly above ambient pressure, some air may leak from the isolator 10 through the conduit 13.

By way of example only, the conduit 13 may be in the region of two feet along the length of the conduit and the opening 15 may be in the region of 18 inches in diameter. The air holes 27 may be positioned between one-fourth and one-half inch apart.

As shown in FIG. 2, a flap offlexible synthetic plastic material 28 is secured by welding along a weld line 29 above the opening 15, and is weighted by a metal bar 30 so as to hang across the opening 15. In combination with the slight positive pressure within the isolator and the flow of air from the apertures 27, the weight 30 maintains the flap 28 in a good seal with the wall ll around the opening 15. The flap is moved to one side when it is desired to pass objects into the isolator 10 through the conduit 13. As an alternative to the flap 28, a loose inner conduit extending into the isolator from the opening 15 may be provided and may be sealed, for example by a plastic zip fastener (not shown). This inner conduit (shown in s different arrangement in FIG. 4 described hereinafter) is entirely within the enclosure member of the isolator and is operated from within the isolator by manipulating means such as rubber gloves and sleeves extending into the isolator, and integral with the wall thereof. Such gloves conventionally extend the length of the operators arms and allow an operator to stand outside the isolator but to extend his arms (in the gloves) within the enclosure to manipulate objects therein. Thus the flap 28 can be opened and closed without breaking the isolation of the enclosure.

The apparatus is particularly useful in providing a method for introducing sterile supplies into a surgical isolator, for example for introducing the sterile surgical instrument pack which is commonly available in operating theatres. This pack consists of a tray of cardboard, metal or plastic containing the instruments to be used and surrounded by one or more wraps of paper or cloth.

The air emerging from the entry port provides a cone of sterile air in which the outer wrap of the sterile package can be partially removed by the circulating nurse. The scrub nurse. using the gloves and sleeves which are continuous with the wall of the isolator enclosure, reaches through the opening 15 from the inside of the isolator and grasps the sterile end of the package, the non-sterile end of the package being held by the circulating nurse whose arms and hands are pushed into the conduit 13 from the end outside the isolator. The scrub nurse reaching into the conduit from the isolator end then introduces the sterile package into the isolator while the circulating nurse removes the outer protecting wrap from the conduit.

In practice the conduit may be either disposable and form part of the isolator for sterilisation purposes. or may be a separate item which can be sterilised in an autoclave by the hospital staff. The isolator itself is sterilised by gamma-radiation, as is also the conduit when permanently attached to the isolator.

A number of modifications may be made to the apparatus shown in the figures. For example the air arranged to flow over at least part of the inner surface of the conduit may be arranged to flow from inside the isolator 10, being directed in the appropriate flow pattern by channels (not shown) in the opening 15.

In another modification. means for distributing the air from the ribs 22 may be provided in the form of an inner cloth wall (not shown) in FIGS. 1 and 2 extending from the ring 23 to the weld line 21, and serving the purpose of distributing evenly the air passing into the conduit 13. One preferred embodiment of a port according to the invention in which an inner cloth wall is used to distribute the air evenly will now be described with reference to FIGS. 3 and 4. In these figures, those elements which correspond to elements shown in FIGS. 1 and 2 will be referred to by like reference numerals.

As can be seen in FIGS. 3 and 4 the general configuration of the transfer port 12 is similar to that of FIGS. 1 and 2. The transfer port 12 is partially supported by rings 31 and 32 coupling a frame 33 to eyelets 34 attached to the isolator wall 11, or alternatively (or in ad dition) by a fold of plastic 35 suspending the port 12, from a rod 36. The port shown in FIGS. 3 and 4 may, for example, be shorter than that of FIGS. I and 2, for example Ift long along the conduit. Other differences in layout. relative to the embodiments of FIGS. 1 and 2. include the provision of a rear circular rib 23. and two weld lines 21' extending through the ribs 23 and 23' to divide the upper and lower sets of ribs. The upper and lower sets of ribs are supplied with sterilised air from an inlet chamber 37 coupled to the pipe 24 and communicating with the ribs 21, 23 and 23' through two inlet ports 38 and 39. The inlet chamber 37 also supplies air to the main enclosure member of the isolator through an inlet port 40.

The main functional modification of the transfer port of FIGS. 3 and 4 is that the inner wall 19 is formed of canvas in place of the synthetic plastics material of FIGS. 1 and 2. The outer wall 20 continues to be made of synthetic plastics material and is bonded to the canvas at the weld lines in the same manner as when both walls were made of synthetic plastics.

In FIG. 4, the inner edges of the walls 19 and 20 at the isolator end of the conduit 13 are shown diagrammatically in exploded form. In practice, in this example. the edges of the walls 19 and 20, the further conduit 41, and the opening in the wall 11, are all welded together at a single weld line produced by heat and pressure welding of the plastic material.

The advantage of the inner canvas wall is that the openings for the sterilised air are far more numerous than with the perforated synthetic plastics material. Because of the relative stiffness of the canvas. the ribs 22 can made much wider while providing a relatively smooth curve to the inner surface of the conduit. As

the ribs 22 are wider, almost the whole inner surface of the conduit 13 is a live" surface. in that it passes sterilised air. This produces an even flow of air over the inner surface of the conduit.

As has been mentioned previously. the embodiment of FIGS. 3 and 4 includes a further conduit 41 of single walled synthetic plastics material. This further conduit 41 is a continuation of the conduit 13, and extends inside the enclosure member of the isolator 10. The con duit 41 serves to shut-off the conduit 13 from the enclosure when the conduit 13 is not in use for transferring objects.

As has been mentioned in connection with the embodiments of FIGS. 1 and 2, the air supplied to the transfer port may initially be unsterilised and may be sterilised by passing through a filter contained in the transfer port. In one convenient arrangement. an internal filter may be provided in the transfer port by a glass wool filter mat positioned between the inner and outer walls of the transfer port and formed on the interior surface of the canvas inner wall of the transfer portv Thus the air circulating between the filter mat and the outer wall of the transfer port may be unsterile, but is rendered sterile by passing through the glass wool filter mat to the openings in the canvas wall.

In some arrangements embodying the invention. the outer wall of the conduit. for example the outer wall 20 in FIGS. 3 and 4, may be made of rigid material such as rigid synthetic plastic material the configuration being otherwise as shown in the figures. Alternatively. in some arrangements. the conduit may be self supporting by virture of the rigid outer wall and the rib configuration may be dispensed with. In both cases. the inner wall 19 may remain of canvas or perforated synthetic plastics material, or the inner wall may also be made of rigid material.

I claim:

1. An isolator comprising:

an isolator enclosure member;

a transfer conduit for passage of objects into said isolator enclosure member. said conduit communicating at one end with the interior of said enclosure member and having its other end external to said enclosure member, and at least part of said conduit having inner and outer walls spaced apart from each other when the conduit is in use;

air supply means for supplying sterilized air to the space between said inner and outer walls of said conduit; said inner wall of said conduit defining an array of openings through said inner wall for directing a flow of sterilized air over that part of the inner surface of said conduit which adjoins said external end of said conduit in a flow pattern for preventing entry of unsterilized air into said conduit; and

a closure member situated within said enclosure member for closing off said conduit from the interior of said enclosure member when said conduit is not in use for passage of objects; said closure member comprising a further conduit of flexible material extending from the first conduit into the interior of the enclosure member.

2. An isolator comprising:

an isolator enclosure member of a size such as to allow surgical operations or other medical activities to be carried out within the enclosure member;

a transfer conduit for passage of surgical instrument packs and other sterilized objects into said isolator enclosure member, said conduit communicating at one end with the interior of said enclosure member and having its other end external to said enclosure member, said conduit having a length along the axis of said conduit at least equal to half the width of said conduit at its narrowest part, and at least part of said conduit having inner and outer walls spaced apart from each other when the conduit is in use;

air supply means for supplying sterilized air to the space between said inner and outer walls of said conduit;

said inner wall of said conduit defining an array of openings through said inner wall for directing sterilized air from said space between said walls into said conduit, and said openings being arranged in an array which continues along the inner surface of said conduit to an extent sufficient for providing an overall outward flow of sterilized air over said inner surface of said conduit for preventing entry of unsterilized air unto said conduit by turbulence effects at the edge of said external end of said conduit.

3. An isolator according to claim 2 wherein the conduit walls are made of flexible material, and the inner and outer walls are joined together at intervals to provide inflatable ribs such that the conduit is at least partially self-supporting in an open configuration when inflated through the air inlet.

4. An isolator according to claim 2 wherein the outer wall of the conduit is formed of rigid material.

5. An isolator according to claim 4 wherein the inner wall of the conduit is formed of rigid material.

6. An isolator according to claim 2, wherein the inner wall of the conduit is made of woven fabric, the said array of openings being provided by the intersticies in the woven fabric.

7. An isolator according to claim 6 wherein the said woven fabric is canvas.

8. An isolator according to claim 2 including a layer of air filtering material positioned between the inner and outer walls of the conduit, and contiguous with the inner wall of the conduit.

9. An isolator comprising:

flexible, inflatable, isolator enclosure member of a size such as to allow surgical operations or other medical activities to be carried out within the enclosure member;

a transfer conduit for passage of surgical instrument packs and other sterilized objects into said isolator enclosure member. said conduit communicating at one end with the interior of said enclosure member and having its other end external to said enclosure member. said conduit having a length along the axis of said conduit at least equal to half the width of said conduit at its narrowest part, and at least part of said conduit having inner and outer walls spaced apart from each other when the conduit is in use;

a closure member situated within said enclosure member for closing off said conduit from the inte rior of said enclosure member when said conduit is not in use for passage of objects; and

air supply means for supplying sterilized air to the space between said inner and outer walls of said conduit;

said inner wall of said conduit defining an array of openings through said inner wall for directing sterilized air from said space between said walls into said conduit. and said openings being arranged in an array which continues along the inner surface of said conduit to an extent sufficient for providing an overall outward flow of sterilized air into said conduit by turbulence effects at the edge of said external end of said conduit.

10. A isolator according to claim 9 in which the closure member comprises a flexible sheet member of synthetic plastic material and a weighting member attached to the sheet member for holding the sheet member across the inner end of the transfer conduit.

11. A transfer apparatus for an isolator comprising:

a transfer conduit for passage of surgical instrument packs and other sterilized objects into an isolator enclosure member, said conduit having a length along the axis of said conduit at least equal to half the width of said conduit at its narrowest part, and at least part of said conduit having inner and outer walls spaced apart from each other when the conduit is in use; and

air supply means for supplying sterilized air to the space between said inner and outer walls of said conduit;

said inner wall of said conduit defining an array of openings through said inner wall for directing sterilized air from said space between said walls into said conduit, and said openings being arranged in an array which continues along the inner surface of said conduit to an extent sufficient for providing an overall outward flow of sterilized air over said inner surface of said conduit for preventing entry of unsterilized air into said conduit by turbulence effects at the edge of said end of said conduit.

12. A transfer apparatus according to claim 11 wherein the conduit walls are made of flexible material, and the inner and outer walls are joined together at intervals to provide inflatable ribs such that the conduit is at least partially self-supporting in an open configu ration when inflated through the air inlet.

13. A transfer apparatus according to claim 11 wherein the inner and outer walls of the conduit are made of flexible synthetic plastics material.

14. A transfer apparatus according to claim ll wherein the outer wall of the conduit is formed of rigid material.

15. A transfer apparatus according to claim 11 wherein the inner wall of the conduit is formed of rigid material.

16. A transfer apparatus according to claim 11 wherein the inner wall of the conduit is made of woven fabric, the said array of openings being provided by the intersticies in the woven fabric.

17. A transfer apparatus according to claim 11 wherein the said woven fabric is canvas.

18. A transfer apparatus according to claim 11 including a layer of air filtering material positioned between the inner and outer walls of the conduit and continguous with the inner wall of the conduit.

* r 4: a: :r 

1. An isolator comprising: an isolator enclosure member; a transfer conduit for passage of objects into said isolator enclosure member, said conduit communicating at one end with the interior of said enclosure member and having its other end external to said enclosure member, and at least part of said conduit having inner and outer walls spaced apart from each other when the conduit is in use; air supply means for supplying sterilized air to the space between said inner and outer walls of said conduit; said inner wall of said conduit defining an array of openings through said inner wall for directing a flow of sterilized air over that part of the inner surface of said conduit which adjoins said external end of said conduit in a flow pattern for preventing entry of unsterilized air into said conduit; and a closure member situated within said enclosure member for closing off said conduit from the interior of said enclosure member when said conduit is not in use for passage of objects; said closure member comprising a further conduit of flexible material extending from the first conduit into the interior of the enclosure member.
 2. An isolator comprising: an isolator enclosure member of a size such as to allow surgical operations or other medical activities to be carried out within the enclosure member; a transfer conduit for passage of surgical instrument packs and other sterilized objects into said isolator enclosure member, said conduit communicating at one end with the interior of said enclosure member and having its other end external to said enclosure member, said conduit having a length along the axis of said conduit at least equal to half the width of said conduit at its narrowest part, and at least part of said conduit having inner and outer walls spaced apart from each other when the conduit is in use; air supply means for supplying sterilized air to the space between said inner and outer walls of said conduit; said inner wall of said conduit defining an array of openings through said inner wall for directing sterilized air from said space between said walls into said conduit, and said openings being arranged in an array which continues along the inner surface of said conduit to an extent sufficient for providing an overall outward flow of sterilized air over said inner surface of said conduit for preventing entry of unsterilized air unto said conduit by turbulence effects at the edge of said external end of said conduit.
 3. An isolator according to claim 2 wherein the conduit walls are made of flexible material, and the inner and outer walls are joined together at intervals to provide inflatable ribs such that the conduit is at least partially self-supporting in an open configuration when inflated through the air inlet.
 4. An isolator according to claim 2 wherein the outer wall of the conduit is formed of rigid material.
 5. An isolator according to claim 4 wherein the inner wall of the conduit is formed of rigid material.
 6. An isolator according to claim 2, wherein the inner wall of the conduit is made of woven fabric, the said array of openings being provided by the intersticies in the woven fabric.
 7. An isolator according to claim 6 wherein the said woven fabric is canvas.
 8. An isolator according to claim 2 including a layer of air filtering material positioned between the inner and outer walls of the conduit, and contiguous with the inner wall of the conduit.
 9. An isolator comprising: flexible, inflatable, isolator enclosure member of a size such as to allow surgical operations or other medical activities to be carried out within the enclosure member; a transfer conduit for passage of surgical instrument packs and other sterilized objects into said isolator enclosure member, said conduit communicating at one end with the interior of said enclosure member and having its other end external to said enclosure member, said conduit having a length along the axis of said conduit at least equal to half the width of said conduit at its narrowest part, and at least part of said conduit having inner and outer walls spaced apart from each other when the conduit is in use; a closure member situated within said enclosure member for closing off said conduit from the interior of said enclosure member when said conduit is not in use for passage of objects; and air supply means for supplying sterilized air to the space between said inner and outer walls of said conduit; said inner wall of said conduit defining an array of openings through said inner wall for directing sterilized air from said space between said walls into said conduit, and said openings being arranged in an array which continues along the inner surface of said conduit to an extent sufficient for providing an overall outward flow of sterilized air into said conduit by turbulence effects at the edge of said external end of said conduit.
 10. A isolator according to claim 9 in which the closure member comprises a flexible sheet member of synthetic plastic material and a weighting member attached to the sheet member for holding the sheet member across the inner end of the transfer conduit.
 11. A transfer apparatus for an isolator comprising: a transfer conduit for passage of surgical instrument packs and other sterilized objects into an isolator enclosure member, said conduit having a length along the axis of said conduit at least equal to half the width of said conduit at its narrowest part, and at least part of said conduit having inner and outer walls spaced apart from each other when the conduit is in use; and air supply means for supplying sterilized air to the space between said inner and outer walls of said conduit; said inner wall of said conduit defining an array of openings through said inner wall for directing sterilized air from said space between said walls into said conduit, and said openings being arranged in an array which continues along the inner surface of said conduit to an extent sufficient for providing an overall outward flow of sterilized air over said inner surface of said conduit for preventing entry of unsterilized air into said conduit by turbulence effects at the edge of said end of said conduit.
 12. A transfer apparatus according to claim 11 wherein the conduit walls are made of flexible material, and the inner and outer walls are joined together at intervals to provide inflatable ribs such that the conduit is at least partially self-supporting in an open configuration when inflated through the air inlet.
 13. A transfer apparatus according to claim 11 wherein the inner and outer walls of the conduit are made of flexible synthetic plastics material.
 14. A transfer apparatus according to claim 11 wherein the outer wall of the conduit is formed of rigid material.
 15. A transfer apparatus according to claim 11 wherein the inner wall of the conduit is formed of rigid material.
 16. A transfer apparatus according to claim 11 wherein the inner wall of the conduit is made of woven fabric, the said array of openings being provided by the intersticies in the woven fabric.
 17. A transfer apparatus according to claim 11 wherein the said woven fabric is canvas.
 18. A transfer apparatus according to claim 11 including a layer of air filtering material positioned between the inner and outer walls of the conduit and continguous with the inner wall of the conduit. 